1. Field of the Invention
The invention relates to a hydrocarbon conversion process. The invention specifically relates to the alkylation of hydrocarbons such as aromatics or paraffins to produce useful chemicals and motor fuel. The invention is primarily directed to a process for the solid bed alkylation of isobutane to produce C.sub.8 isoparaffins useful as motor fuel blending components.
2. Related Art
Large amounts of high octane gasoline are produced by alkylation of isobutane with butenes or propylene. This significantly increases the value of the C.sub.4 feed hydrocarbons. Large amounts of valuable aromatic hydrocarbons including cumene, ethylbenzene and C.sub.10 -C.sub.15 linear alkylaromatics are produced by the alkylation of benzene with olefins of the appropriate carbon number.
The variety of possible feed reactants and the passage of time has led to the development of a number of effective alkylation technologies which are employed in large scale commercial facilities. One of the most widely used processes for the production of motor fuel is HF alkylation as described in U.S. Pat. No. 4,139,573 issued to D. B. Carson. This reference provides an overview of the HF alkylation process and also describes the use of indirect heat exchange to vaporize butanes as a means to remove heat from the reaction zone.
U.S. Pat. No. 3,893,942 issued to C. Yang discloses a method of increasing the stability of zeolitic alkylation catalysts by including a Group VIII metal hydrogenation agent and periodically hydrogenating partially deactivated catalyst by contact with a hydrogen containing gas.
U.S. Pat. No. 4,849,569 issued to L. A. Smith, Jr. describes a solid bed alkylation process employing catalytic distillation to react a C.sub.2 -C.sub.10 olefin with an aromatic hydrocarbon. In catalytic distillation the heat of reaction is allowed to vaporize a portion of the liquid phase reactants present in the reaction zone thus removing heat from the reaction zone. This reference describes the use of aluminosilicate molecular sieves as a catalyst. U.S. Pat. No. 4,950,834 issued to R. P. Arganbright et al. describes the production of cumene by the reaction of propylene and benzene using solid catalysts in a catalytic distillation zone. The two catalysts may contain Y zeolite or omega zeolite.
Yet another design for a solid catalyst alkylation process is described in U.S. Pat. No. 5,157,196. This process uses a moving bed of catalyst, with the catalyst being loaded with a paraffin substrate outside of the reactor and then passing through the reactor and into a product recovery zone to produce motor fuel alkylate.
U.S. Pat. No. 5,190,730 issued to L. A. Smith, Jr. et al. provides a process in which the heat released by an exothermic oligomerization or etherification reaction is used to vaporize reactants. The reactants are preheated and passed through a plug flow prereactor at conditions such that any heat released by the reaction will cause vaporization of reactants. That is, this prereactor is maintained at the boiling point of the reaction mixture, which allows the temperature of the reactor to be regulated by adjustments to the reactor pressure.
U.S. Pat. No. 4,540,831 issued to B. A. Briggs presents a similar reaction system in which a bed of catalyst within a reaction vessel is maintained at a pressure which allows heat released by an exothermic reaction to vaporize reactants, with the vapors being condensed by an internal overhead condenser and returned to the catalyst bed for withdrawal from the bottom of the vessel.